The invention relates to a process for the production of pig iron from fine ore, in which the fine ore is pre-reduced in one or more reduction units and the resulting sponge iron is then melted down and finally reduced in a melt-down gasifier with the aid of at least one plasma burner and a solid carbonaceous reducing agent.
In a process for the reduction of iron ore, known as the plasma melt process, there is a prereduction of the iron ore and a subsequent melting reduction in a melt-down gasifier. Prereduction takes place with the aid of the gas produced in the melt-down gasifier. The prereduced sponge iron is fed into the lower part of the melt-down gasifier via the melting and slag hearth. One or more plasma burners also act in this part and supply at least part of the heat required for melting the sponge iron. The plasma burners also serve to introduce coal dust into the melt-down gasifier and this is used as the reducing agent for the sponge iron. Coke is introduced from above into the melt-down gasifier and forms a solid gas and liquid-permeable bed, in which reduction takes place. Immediately following the introduction of the sponge iron into the melting and reducing zone of the melt-down gasifier, this is melted and completely reduced. The molten iron and slag collect in the hearth provided for this purpose at the bottom of the melt-down gasifier and are removed at appropriate time intervals. This known process is subject to limitations in that the coal must be ground to dust before it can be supplied via the plasma burners and because it is necessary to use relatively expensive coke for producing and maintaining the static bed.
EP No. 0 063 924 A2 discloses a process for reducing and melting fine ore, in which a prereduction is also carried out and the prereduced ore together with the heated air is introduced laterally into the melt-down gasifier via blast nozzles. Solid carbonaceous material is introduced from above into the melt-down gasifier and forms the static bed therein. Upstream of the blast nozzles the temperature rises to approximately 2000.degree. to 2500.degree. C. and cavities form there in the static bed, in which the iron ore melts and is finally reduced. However, a considerable heat quantity is required for this, so that the heat supplied is often not adequate to completely melt and reduce the ore. As ore is not only blown into the lower part of the melt-down gasifier, but also and more particularly into the central part thereof, where melting takes place, the complete gasifier region below this must be kept at a temperature such that the downwardly dripping molten iron does not solidify. Thus, here again there are problems in covering the corresponding heat requirements. It is much more advantageous to supply the necessary heat by plasma burners instead of by heated air.
On the basis of the known plasma melt process, the problem of the present invention is to so improve said process that neither coke, nor ground coal are required as starting materials and instead operation is possible with coal of any type and form.